1. Field of the Invention
The present invention relates to fluid nozzles and particularly to a fluid nozzle including a base metal member having a rear portion covered with a ceramic coating.
2. Description of the Related Art
Water jet processing machines perform cutting or other operations using a water jet (a liquid column made of a fluid jet), which is a high-pressure fluid (for example, water or highly pure water). The water jet processing machines are characterized in that they produce a relatively small cutting width and less frequently cause seizure of a material or change the composition of a material. Thus, the water jet processing machines are used to perform operations such as to cut expensive materials or to process fine grooves.
These days, in order to minimize processing steps and the amount of materials that are to be wasted during processing, precision finished products that do not require finishing using a water jet have been increasingly demanded.
Thus, a processing apparatus that processes a material using a laser beam guided by a water jet has been developed (hereinafter such an apparatus is referred to as a “water beam processing machine” (for example, see Japanese Patent No. 5220914). The water beam processing machine is advantageous in that it can highly precisely finish products since the material is negligibly deformed by heat.
To highly precisely finish products in water jet processing, a water jet from a water-jet fluid nozzle is required to be ejected through the nozzle center so as to be parallel to the nozzle axis while the water jet keeps a stable liquid-beam diameter.
To date, a water-jet-processing fluid nozzle in which a nozzle orifice made of a diamond is embedded in a nozzle body that fixes a nozzle chip thereto (for example, see FIG. 2 of Japanese Unexamined Patent Application No. 2009-78313) is known.
In the fluid nozzle described in Japanese Unexamined Patent Application No. 2009-78313, a portion of the nozzle body that is exposed to a high-pressure fluid (high-pressure water) is made of a resin material in order that a workpiece can be prevented from being contaminated by a water jet into which metal in the nozzle body is dissolved and mixed as a result of the high-pressure water coming into contact with the nozzle body.
However, the strength of the fluid nozzle described in Japanese Unexamined Patent Application No. 2009-78313, which includes a resin portion in the nozzle body that fixes the nozzle chip thereto, may be insufficient to hold the nozzle orifice for use in highly precise finishing of products. Thus, disadvantageously, this fluid nozzle is insufficient to precisely position the nozzle orifice and firmly and stably hold the nozzle orifice.
In some cases, water hammer occurs in the nozzle body during the supply of a high-pressure water or when the supply of the high-pressure water is stopped, exerting a strong impact force on the nozzle body. In the case where the nozzle body is used in a laser beam processing machine such as the one disclosed in Japanese Patent No. 5220914, the nozzle body is required to have such rigidity and durability as to be capable of stably holding the nozzle chip since the nozzle chip and its vicinity may be damaged as a result of being exposed to a strong laser beam.
In the case where the nozzle body is damaged by the impact pressure and the laser beam, the flow of the high-pressure water around the inlet port of the nozzle chip is disturbed and becomes irregular and unstable, conceivably failing to form a stable water jet.